Contributions from the Queensland Herbarium

QUEENSLAND HERBARIUM
DEPARTMENT OF PRIMARY INDUSTRIES
BRISBANE

CONTRIBUTIONS

FROM THE

QUEENSLAND HERBARIUM

No.3 A Cytological Study of Lantana montevidensis (Spreng.)

Brig. in Queensland.

By R. J. F. HENDERSON

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Issued 30th=September, 1969

«QUEENSLAND HERBARIUM
DEPARTMENT OF PRIMARY INDUSTRIES
BRISBANE

CONTRIBUTIONS

FROM THE

QUEENSLAND HERBARIUM

No. 3 A Cytological Study of Lantana montevidensis (Spreng.)

Brig. im Queensland.

By R. J. F. HENDERSON

Issued 30th=September, 1969

Contributions from the Queensland Herbarium, No. 3

A CYTOLOGICAL STUDY OF LANTANA MONTEVIDENSIS
(SPRENG.) BRIQ. IN QUEENSLAND

By R. J. F. HENDERSON

Queensland Herbarium, Brisbane

SUMMARY

Chromosome numbers in L. montevidensis are 2n (3x) = 36 for a sterile exclusively
garden form, and 2n (4x) = 48 for a fertile form that has become widely naturalized.

INTRODUCTION

Lantana montevidensis, commonly called Creeping Lantana, occurs in
Queensland in two well marked forms. One, here designated the wild form, fruits
freely, has darker purplish flowers, has run out from cultivation and is now
naturalized to the extent of being a troublesome weed in a few areas. The other
form, here called the garden form, does not ripen fruit and is propagated
vegetatively, has slightly paler flowers, and is confined to garden culture.

Previous cytological investigations principally by Paterman (1938), Singh
(1951), Tandon & Bali (1955), Sen & Sawhni (1955), Natarjan & Ahtya (1957),
Raghavan & Arora (1960) showed the genus Lantana to be dibasic with base
numbers 11 & 12 and that there are polyploid series based on both these numbers.
L. montevidensis was reported to have a chromosome complement of 36 by
Raghavan & Arora (op. cit.).

MATERIALS AND METHODS

The behaviour of meiotic chromosomes was studied in pollen mother cells
(PMC) squashed in 45% acetic acid after staining in alcoholic hydrochloric
acid—carmine according to Snow (1963). Mitotic chromosomes were studied in
root-tip squashes from vegetative cuttings collected in the field and grown under
glasshouse conditions. Excised material was immersed in saturated aqueous
para-Dichlorcbenzene for three hours prior to fixation and staining as outlined

2 CONTR. Op HERB. No. 3

for PMC. Voucher specimens for counts are held in the Queensland Herbarium.
(Wild form—Henderson H448 (BRI.077557); Garden form—Henderson H449
(BRI.077558) ).

Pollen viability was estimated from ten counts of stained grains (excluding
stained microspores) in glycerine—lactophenol—aniline blue according to Baylis
(1954). Irregularities in the usually smooth walls of some of these stained pollen
grains suggest that actual viability is less than that given.

RESULTS

The wild form of L. montevidensis is tetraploid with a somatic chromosome
number of 48 (figs. [A and 2A). This appears to be a new number for the species.
In the zygotene stage hexavalents, quadrivalents, trivalents, univalents as well as
bivalents may be formed. Univalents and multivalent associations occur in most
dividing cells.. At metaphase I, up to four univalents have been observed not
migrating to the plate. At anaphase I, 24 chromosomes may migrate to each pole
but a 25~-23 separation has been observed. In addition, some cells have been
observed where a number of chromosomes remain unrelated to either main group
at the poles. Miucrospore formation after the tetrad stage results from further
lagging of these chromosomes.

Chromosome behaviour is more consistent with autotetraploidy than
allotetraploidy, while the frequency of univalents and multivalents suggests that
reciprocal translocations have occurred following the rise in ploidy level.

Reduced pollen fertility results from these meiotic abnormalities but despite
this, the production of fertile seed is high. Pollen viability is approximately
65%, the fertile grains being (26—) 29-35» in diameter,

The garden form of L. montevidensis is triploid with a somatic chromosome
number of 36 (figs. 1B and 2B), which agrees with that reported for Indian
plants by Raghavan & Arora (op. cit.). However, contrary to their findings,
chromosome behaviour at meiosis is irregular in Queensland plants.

At the zygotene stage, trivalents and univalents as well as bivalents are formed.
No quadrivalents were observed. At metaphase I, up to five univalents were
observed not migrating to the plate. At anaphase I, 18 chromosomes may move
to each pole, but one or two usually lag. By anaphase II, the lagging daughter
chromosomes are located well away from the four main groups and consequently
lead to the formation of a relatively large number of microspores.

The frequency of trivalent formation suggests the relative similarity of the
third set of chromosomes to the supposed diploid complement, but may only
indicate accumulated reciprocal translocations in the chromosome complement
over a period of cultivation and vegetative reproduction.

CYTOLOGICAL STUDY OF LANTANA MONTEVIDENSIS

RIF,

Fic. 1. Meiotic chromosomes at diakinesis in Lantana montevidensis, A, wild form (1 VI,
11V, 1, 1401, 71); B, garden form (5 UJ, 6, 91).

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Fig. 2. Mitotic chromosomes in root-tip squashes of Lantana montevidensis, A, wild form,
2n == 48; B, garden form, 2n = 36,

4 CONTR. Op HERB. No, 3

Pollen viability is always less than 6%, the stained grains varying from 22
to 31 in diameter. The presence of some viable pollen confirms the statement
made by Lewis (1967) that triploids in general have low fertility but contrary to
common belief are rarely if ever completely sterile.

With regard to seed production, the plant behaves as might be expected of
a normal triploid (as opposed to an apomictic triploid) with no viable seed
appearing to be set, although occasionally an ovary will increase in size for a
time after flowering.

At magnifications of about 1250 the chromosomes of both forms are quite
small. This, unfortunately, does not allow for detailed study of chromosome
morphology which may have been useful in postulating relationships between
these two forms.

REFERENCES

Baylis, G. T. S. (1954). Chromosome number and Distribution of Solanum aviculare Forst.
and §. faciniatum Ait. Trans. Roy. Soc. N.Z. 82: 639-643.

Lewis, H. (1967). The Taxonomic Significance of Autopoidy. Taxon 16 (4): 267-271.

NATARAJAN, A. T. & Auntya, M. R. (1956). Cytotaxonomical] studies in the genus Lantana.
Ind, Bot, Soc. 36: 35-45.

PATERMAN, JT. (1938) in DaRLINGTon, C. B. & WYLIE, A. P. (1955). Chromosome Atlas of
Flowering Plants. London: Allen & Unwin.

RAGHAVAN, R. S. & ARorA, C. M. (1960). Morphological and Cytological studies in the genus
Lantana L. Bull. Bot. Surv. Ind. 2: 299-303.

SEN, N. K. & SAWHNI, V. M. (1955). Triploid, Tetraploid and Pentaploid Lantana. Sci. &
Cult, 20: SS58-—5S59.

SINGH, B. (1951). Chromosome numbers in some flowering plants. Curr. Sci. 20: 105.

SNow, R. (1963). Alcoholic Hydrochloric acid—Carmine as a stain for chromosomes in
squash preparations. Stain Tech, 38: 9-13.

TANDON, 8S. L. & BALI, P. N. (1955). Morphological and Cytological studies of a Diploid and
naturally occurring Triploid in Lantana camara L. Ind. J. Hort. 12: 1-S.

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